ESA JUICE RED BOOK — PART 4

The Galileo spacecraft also discovered an internal magnetic field at Ganymede, a unique feature for a satellite in the Solar System. Ganymede and Europa are believed to be internally active, due to a strong tidal interaction and other energy sources. They are straddled by Io and Callisto, and thus JUICE’s study of the diversity of planetary environments represented by the four satellites should reveal the physical and chemical mechanisms driving the evolution of the Jovian system

JUICE is an ESA-led mission possessing broad appeal and strong support from planetary scientists. The ten scientific instruments have diverse science teams from across the planetary science community, including co-investigators from many nations to demonstrate the international support for this next step in the exploration of the outer solar system. NASA foresees to contribute with one PI instrument (the UV imaging spectrograph, UVS) and hardware for two European-provided instruments: the ice-penetrating radar RIME, and the plasma package PEP. JAXA foresees to contribute with hardware for various European-provided instruments

The Galilean satellites are known to have thin atmospheres, technically exospheres (McGrath et al., 2004), produced by ion-induced sputtering and sublimation of the surface materials. Thus their properties are indicative of processes and composition at the surfaces (see also Section 4.1.3). The presence of an O2 atmosphere at Europa has been inferred from measurements of UV emissions, and similar evidence for local H2O plume sources now await confirmation; Na and K have also been measured at Europa, in ground-based observations

JUICE will significantly contribute to our understanding of the atmospheres of the icy satellites, their origin and evolution, as well as the chemical composition of their surfaces, by observing the exospheres of Europa, Callisto and Ganymede through remote monitoring, imaging of the aurora, multi-wavelength limb scans and stellar occultation, and directly by in situ measurements by sensors of the particle packages from low orbits and fly-bys